The problem with non-EFI (PC) graphics cards is that they aren't initialized by the Mac boot sequence, so the screen remains black until a compatible driver is loaded. The built-in default OS X nVidia driver supports older-generation graphics cards like the GTX 680 (you still won't have a bootscreen, but the OS installer and the OS itself will never be a black screen, and you won't have to manually install any drivers). However, the built-in driver doesn't support the newest PC cards (such as nVidia's GTX 7xx Maxwell architecture or higher), so here's what you need to do when you want a very modern graphics card: Initial setup and preparation for installing the PC graphics card: Disable FileVault (whole disk encryption) if you have it. It does NOT work with non-EFI graphics cards and you won't be able to boot. Unfortunate but true. That's because it cannot talk to the graphics card to generate the password GUI, so you can't even type it blindly. It simply does not work. You will not get ANYWHERE if you have disk encryption enabled. Trust me, this is a fact. People online who have said they could type it blind used very old OS X versions that used to be capable of doing it. Not possible anymore. Pick up your old EFI card (such as the GT120 that came with most classic Mac Pros). (PS: Always keep this card somewhere in case of future emergencies or OS reinstalls). Boot the Mac. Go into System Preferences : Sharing, and enable Screen Sharing. On your iPhone, install the free "VNC Viewer" by RealVNC (https://itunes.apple.com/us/app/vnc-viewer/id352019548?l=en&mt=8). It supports Apple's screen sharing protocol. You will need this app a lot (or screen sharing via another Mac) in the future. Also go into the Mac's System Preferences : App Store, and disable "Install OS X updates" and "Install system data files and security updates". You CANNOT let the OS auto-install anything that can change the OS X build number, because the nVidia driver is tied to the build number, so if you update the OS (regardless of if it is "just" a "security update" and not a new "10.11.x whatever"), it will disable the nVidia driver and your display stops working! This cannot be stressed enough! Find the correct NVIDIA Web Driver. The official nVidia website is a mess, so use this instead to locate the correct installer for your OS version: http://www.macvidcards.com/drivers.html. Read the instructions on that page if you don't know which OS version you are running. And if there are multiple drivers in a row for the same OS version, pick the rightmost one (it is the newest driver). Now install the NVIDIA Web Driver. It adds support for the latest nVidia cards. When the installer tells you to reboot, don't click Reboot yet. Before rebooting, open a Terminal and type: sudo nvram boot-args="nvda_drv=1" to be absolutely sure that the nvidia driver is the active one. Sometimes the initial installer failed to activate it for me, so I had to do this. Now press the Reboot button, and your GT120 (or whatever EFI card you have) should still work. But it now uses the nVidia driver. Shut down the machine, and remove the GT120 and put the PC graphics card in there. Plug in the extra power cables (if your card needs them; most PC cards do). Your Mac Pro supports 2x6-pin (75 watts each) connectors, and you can buy those special cables online by Googling "mac pro graphics power cable" to find the one for your version of the Mac Pro. And a fair warning: Do not buy any 6-pin to 8-pin converters to try to run "juicier" graphics cards without making sure it's a power-efficient card, because 8-pin ports are able to draw twice as much electricity and can fry your motherboard when connected to a mere 6-pin power cable, so be careful. I prefer PC graphics cards with single/dual 6-pin ports, without any 8-pin ports at all! Boot. The screen should be black until the login screen appears. That's because the driver loads late. Warning: Be aware that if you ever clear NVRAM at startup (via the special key combination), it will reset the "nvda_drv=1" argument and revert to the Apple driver instead, which means your PC graphics card will stop working. If you do that, you'll need to put the old EFI card back in and re-activate the nVidia driver. How to update to a new version of OS X / a new security update: When a new OS update or security update arrives, wait a few days until MacVidCards (the URL above) or various forums state that nVidia has released a driver. It usually takes 1-4 days. Do NOT update in the meantime or you will lose your display. When there's a nVidia driver available for the new update, you can proceed with step 2. Open a Terminal and type: sudo nvram boot-args="nv_disable=1" to disable both Apple's built-in driver and the NVIDIA driver (meaning that no card driver will be loaded AT ALL and the machine will run headless with a software-based graphics driver). This prevents a reboot-loop by the incompatible (older kernel version) NVIDIA driver, and a reboot-loop by the default driver's inability to support the newer GPUs. Note that this step must be done carefully; simply resetting NVRAM will not achieve this and will just lead to Apple's built-in driver being used, so *do not do that*. Download the OS update and let it reboot to install the update. Screen share into the machine (via the iPhone app I mentioned, or via another Mac) and log in. It uses the very slow software graphics driver, so the GUI will be a bit sluggish. Go into the System Preferences panel, and go into the nVidia Driver panel at the bottom. It has a button to check for nVidia driver updates. Press it and let it install the new driver. This is how you get new driver versions (no need to go back to MacVidCards anymore). Do not click the "Restart" button when the driver has been installed. Instead, open a Terminal, and type the following: sudo nvram boot-args="nvda_drv=1" to enable the NVIDIA driver. Note that the updated driver installer actually added that flag already, but it didn't remove our "nv_disable" flag (which means the drivers remain disabled), so that's why this command is necessary. Lastly, click the "Restart" button and enjoy the images on your screen again! This sounds more complex than it is. After a while you get used to it: See a new OS update. Wait a few days. Disable the old driver, reboot, screenshare, install and enable new driver, and reboot. It takes about 15 minutes and isn't much hassle at all. And it's worth it to avoid having to pay for flashing via MacVidCards. The only reason to pay for EFI flashing is if you really, really want FileVault whole-disk encryption, easier access to Windows in boot camp (otherwise you have to reboot to Windows via a "set startup disk" app for both Mac and Windows since you cannot choose a disk at startup), and easier OS reinstalls. But all in all, doing it the DIY way that I've mentioned above, is very easy in my opinion, and feels completely safe since you always have the fallback of the screen sharing access. Just be sure to follow the steps and you can never go wrong. And if you still go wrong, temporarily put in the old EFI graphics cards and you'll be up and running in no time. Enjoy!